Curiosity
by Lanta
Summary: Sara has just arrived in Vegas, and Catherine is determined to find out what her history is with Grissom. AU, GSR.
1. Chapter 1

**Author's Notes**

No, I haven't forgotten Role Reversals and I know it's been a while since my last update, I just really felt like writing something a bit different tonight. So here you are. _Curiosity_ is totally AU, is set just after Sara came to Vegas, and is definitely GSR, although the main characters are actually Catherine and Sara. At the moment I'm intending it to be a one-shot, although if you all like it and want more then I'll think about it.

Disclaimer: CSI isn't mine. If I owned it, I wouldn't be writing fan fiction. Actually, I'm glad I don't own it; the peeps that do can make it a million times better than I ever could.

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Catherine studied the brunette criminalist, who was currently peering into a microscope on the other side of the table. Sara Sidle. Young, probably early thirties at a guess, obviously smart, obviously skilful at her job… and obviously more than just an acquaintance of Grissom's.

She was his friend, and someone he trusted. That's all he had said about her. He'd brought her in to help with the investigation after Holly's death, and afterwards he announced that he had invited her to stay on in Vegas as a crime scene investigator. Not one word about how he knew her.

It wasn't that she had anything against Sara, per se. She just hated not knowing. The curiosity was going to kill her. Oh, she'd tried asking, but his reply had been typically vague: "She's my friend, we've known each other for a long time." Sure, so informative and helpful.

She'd caught a few strands of conversation between Sara and Grissom, something about a seminar, but what did that mean? Had she been a student? An assistant? Were they both lecturers at some convention? She didn't even know if that was where they first met, or whether they'd already known each other at the time.

There was just… something… in the way they spoke to each other. A sort of familiarity, a feeling that they knew each other in a way that was uncommon – okay, unheard of – for Grissom. People weren't supposed to understand Gil Grissom. It was just accepted that he'd be unlike anybody else on the planet. Catherine had prided herself on understanding him better than anyone else, or so she had thought. Now Sara had come along, and it was like she could read his mind, and him hers.

Familiarity… but not necessarily ease. Oh, they were clearly close, and she seemed to spend a lot of her time smiling widely in his direction, but there was just something not quite comfortable between them, as if not everything in their past had been wonderful.

Catherine would give anything to know just what that past had involved.

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It hadn't taken long for Sara to realise that she was being watched. Actually, it hadn't been that unusual over the past few days. After all, she was new around here, and that automatically made her eligible for the inquisitive (or nosy, depending on your irritation levels at the time) attentions of the rest of the lab. But she got the feeling that Catherine Willows' curiosity went beyond simply analysing the new girl.

"Catherine, is there any chance that you could stop staring at me for a few minutes? It's making it difficult to concentrate."

Catherine didn't bother to deny her actions. She chose, instead, to be direct, which was pretty standard for her. "I'm just trying to work out what your relationship is to Grissom."

Sara looked contemplative for a second. "He hasn't told you, then. I'm not surprised."

Two eyebrows lifted. "Then there is something between you. I knew it. What is it?"

Sara shook her head. "Sorry, Catherine. It's not that I have a problem with you knowing, I don't, but Grissom's your friend and I've just met you. It's his job to decide who he tells."

"Sara, this is Grissom we're talking about, one of the most private men on Earth. I'm never going to convince him into telling me. And I can't stand not knowing."

"Sorry, Cath. That's your problem, not mine. Feel free to keep working on Grissom though; you never know, you might get lucky."

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"Cath, Warrick, you've got a DB up near Lake Mead. Sara, Nick, we're going to the suburbs."

There were nods all round the room, and after Grissom gave out what little information he had so far on the cases, Catherine and Warrick left to go to their crime scene. Nick gave a quick "I'll be right with you" to the two remaining occupants of the room before leaving to get something from his locker.

"You know, Griss, Catherine's going out of her mind trying to work out our history."

Grissom raised an eyebrow. "Well, she'll just have to cope with it."

"Griss, she's your friend. You should tell her. You should have told her years ago."

He looked down for a second. "Is that why you left? Because I didn't tell everyone?"

Sara sighed. "Maybe, partially. I left because you didn't make me part of your life, Grissom. You're a workaholic, you always have been. Takes one to know one, I guess. But I was willing to put you ahead of my work, and you…"

"I wasn't. I'm sorry."

"Hey, I've never held it against you, not really. It's just how you are Griss. And you brought me here, didn't you? You gave me that much."

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Curiosity comes in many forms, and has many different motives. Children are often talked about as having 'healthy curiosity,' whilst the phrase 'curiosity killed the cat' has reached the rank of a cliché. It's a natural human occupation, one that has led to many important discoveries throughout history. One particular event at the Las Vegas Crime Lab was to make Catherine Willows very curious indeed, and the subsequent discovery she made, whilst not exactly comparable to that of Isaac Newton, was at least deeply satisfying and more than a little surprising.

The event in question was perhaps not so satisfying, at least from Gil Grissom's point of view. After all, it involved him suffering a fall at a crime scene, and being confined to hospital for three days straight. It was clear early on that his injuries were not very serious, and so Catherine's mind, freed from feeling concern over her friend's well-being, was able to concentrate on wondering just why it was that Sara Sidle was able to fill in all of his forms – insurance, everything – without looking anything up or asking him any questions.

"Sara?"

Both Sara and Catherine looked up to find a woman in possibly her mid seventies looking down on them. Sara's face broke out in a smile and she stood up to greet the newcomer.

"Mrs Grissom! It's good to see you." Her hands moved as she spoke - unnecessarily, as Georgia Grissom was perfectly capable of reading lips, but she appreciated the gesture.

"You too, Sara." Her voice was just slightly too loud, a typical occurrence for a deaf woman speaking. "It's been a long time. I'm glad to see you still remember how to sign."

Sara smiled. "Some of it. I'm out of practice." She turned and gestured to her side. "Have you met Catherine Willows?"

"No, she hasn't," Catherine answered for her, extending a hand and firmly shaking the elder woman's. "It's nice to meet you Mrs Grissom."

"And you, Miss Willows. Gil doesn't tell me much about his life, but he has mentioned you. I remember you have a daughter?"

"Yes – Lindsey, she's seven."

Mrs Grissom smiled at her, then turned back to Sara. "How is he?"

"Complaining like mad about not being allowed out of bed. Other than that, he has a few broken bones and a whole load of bruises. I'm sure the doctors will give you a more detailed account later, but basically he's going to be fine, it'll just take a while. They're checking up on him at the moment; we'll be allowed back in soon."

"You can go in now." The doctor stood at the entrance to the room and smiled at the three women, greeting Mrs Grissom politely and shaking her hand. She thanked him, and all three of them entered to see Grissom looking particularly disgruntled, his back raised at a forty-five degree angle. He brightened up slightly however when he realised that his mother was present.

"Mom!"

She leaned down, hugging him gently. "Now Gil, what have you been doing to yourself?" she scolded lightly as she rose back to a standing position.

"I didn't exactly plan on falling, Mother."

"No, but you weren't looking where you were going either," commented Sara dryly from where she and Catherine were standing at the foot of the bed.

He quickly tried to defend himself. "I was following a blood trail!"

"Yeah, into a hole."

Mrs Grissom smiled. "It's good to see you two together again. I know you kept in touch, but still… I didn't think you'd ever work things out."

Grissom and Sara looked slightly uncomfortably at each other, while Catherine watched eagerly, staying silent in the hope that they would forget her presence and finally give her the answers she craved.

"We're not really together, Mom. We're friends, and Sara works for me now."

Mrs Grissom shook her head. "You two could never be just friends. You were always perfect for each other."

"Thanks," said Sara quietly. "But we have far too many issues between us at the moment. We need to see if we can manage a friendship, before we try anything more."

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"So, Sara."

Sara turned, giving a wry smile to the speaker, who was unsurprisingly Catherine. "I'm surprised you waited this long to ask."

"Well, believe me I'd've asked before, but the babysitter rang to say she had a family emergency and I had to go sort out someone to look after Lindsey. But please, tell me? Neither of you can pretend any longer that you don't have a history."

"Okay, we have a history."

"So, tell."

Sara sighed. "We met just after I graduated from university. I went to one of his seminars. We had coffee afterwards, talked a bit, mostly about forensics. He gave me his card and we kept in touch, I asked him for career advice and he sent me books and journals, encouraged me to keep learning new things. Eventually… eventually we went beyond talking about forensics."

"You dated."

"Took a long time. Couple of years I guess. Grissom is, um, how do I put this…"

"Emotionally detached?"

"You do know him. Yeah, that. I couldn't believe it when he finally took me out for dinner. Then things seemed to move quickly… far more quickly than I expected, really. It got serious, fast."

"It must have done. You seem pretty friendly with his mother. Did you learn sign language for her?"

"Grissom taught me. I loved him, you know. Still do actually. But there were problems. We were in a long-distance relationship, and I was planning on moving to Vegas to be with him. Then, he blew off a trip to see me in order to work – which, I didn't mind too much the first time, I know he's dedicated, but then he did it again, and that wasn't the last time either."

"Doesn't surprise me."

"No. But I was missing him, and I called his cell hoping to speak to him. Brass answered, don't ask me why because I don't know. Turned out he'd never heard of me. So I confronted Grissom, found out that he hadn't told anyone from Vegas."

"So you ended it?"

"Not straight away. But ultimately, yes. I just couldn't stand it any more. I didn't want to hurt him, I knew he'd never intended to hurt me, but I just needed more than he could give me at the time. We kept in touch… we both wanted to keep things open, to leave the potential for a relationship at a later date."

Catherine nodded, smiling as she finally had her appetite sated. "Did you come here to get back together with him?"

"Actually, I came here for the reason you were given – to investigate Holly Gribbs's death. Griss phoned me, told me he needed someone he trusted doing it, so I came. When I saw him, though… I just knew that I couldn't leave again. So when he asked me, I stayed."

Catherine thought for a while, then asked one final question, her eyebrow raised. "When you were filling out forms for him, how did you know his insurance details? Apparently it's years since you've seen him, he could have changed his policy."

"Grissom?"

"Point taken."


	2. Chapter 2

**Author's Note**

People wanted a sequel, so here it is. Hope you like it. Don't expect any more of it; I'm highly unlikely to oblige unless I suddenly get some incredible inspiration.

Summary: Catherine isn't the only one who gets curious.

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Sometimes, curiosity just gets the better of you. It's unavoidable, and often detrimental to your health when the object of your interest isn't happy. Sometimes it's good; occasionally valuable things are learned, and sometimes for those concerned, it's simply a relief to have let someone else in on the secret.

With Catherine's thirst for knowledge finally quenched, Sara found herself relieved to finally have someone in Vegas know of her history with Grissom. Brass suspected, it was true; he may not have been a CSI, but he knew Gil almost as well as Ms Willows, and it was surely only a matter of time until he remembered the phone call, years ago, and connected the dots.

Meanwhile, curiosity was spreading. It was Catherine's fault, of course. She just couldn't resist dropping hints about Sara to the rest of the team; although Sara knew she would never outright tell the others - that was not her decision to make, or Sara's. But Nick and Warrick were reasonably clever, and intuitively knew that there was something going on. As for Greg, the lab tech with an obvious crush on both of the female crime scene investigators, there was just something about some of the comments he'd made to her recently that made her wonder if he'd accidentally heard one of their conversations.

Those conversations had been growing, recently. With constant contact, not to mention the subtle urgings of Grissom's mother - and the non-so-subtle pressure from one Catherine Willows - the desire to move ahead with their relationship had been growing steadily. So far nothing had happened, but that was likely to change, and probably soon.

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"So, you've never told me about your first date."

Sara glanced up from her coffee cup, lifting an eyebrow. "Well, okay, if you must know it was with this guy from college -"

"Your first date with _Grissom_, Sara. Although, it doesn't surprise me that you didn't date till college."

Sara just laughed, and then looked meditative for a second. "It was... nice. Nice restaurant, I think I had some kind of pasta dish. Conversation was very Grissom, doubt you'd have thought much of it, but I liked it. It felt... natural. And since we were in California at the time, Grissom didn't get called into work, which is a definite plus."

Catherine settled into the chair next to her. The door to the break room was closed, keeping their quiet conversation away from potentially prying ears. "Well it was obviously good enough to get a second date."

"And a few more after. Some of them were work-oriented, discussing our jobs and the latest forensic discoveries over lunch or coffee while he was in town for seminars and things. Eventually he started coming down regularly just to see me. I came to Vegas a couple of times, too."

"So, when are you getting back together?" Blunt as always.

"I don't know, Catherine."

"Well, you said you needed time to see if you could be friends, and you certainly seem pretty friendly."

"Catherine..."

"Okay, okay, I'll mind my own business."

Sara wondered absently if that was even possible.

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"So Sara, how's Vegas?"

"I don't know, Greg. As far as I'm aware the city's doing just fine." She shook her head at him, then laughed, her big smile making him incredibly jealous of his boss. He was, after all, still nursing a broken heart from finding out that she and Grissom had a history, and were looking to rekindle it (he'd walked past them talking a week ago). Oh well, there was still always Catherine - strong, independent, beautiful...

Sara decided to take pity on him. "It's fine. I'm enjoying it here. I like my work. Do you have my results for me?"

"And on to business. I like a woman who knows what she wants. I have an ID for you: one Peter Simesfeld, served time for assaulting his son's teacher. Got out of prison last year."

"Thanks Greg." The beaming smile turned on once more as she took the information he offered her and walked out, leaving him sighing with envy.

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Warrick Brown was usually capable of intense concentration whilst working. After all, it was essentially one of the prerequisite abilities of becoming a CSI. But he couldn't deny that at least part of his focus whilst gathering evidence from the Bainsley's bloodstained living room was on the couple currently crouched over the body of Stacey Bainsley.

"It's like they're the same person," observed Nick quietly with a slight shake of his head. "The way they work together."

Warrick nodded in agreement, but didn't answer, instead returning to swabbing the excessive amounts of blood spatter covering the wall next to him. The topic was however, merely put on the shelf, and was returned to as they were changing in the locker room at the end of that shift.

"There's got to be something between them..."

"You really think they're a couple?"

"Yeah... or relatives or something maybe? Man... I couldn't blame him if they are dating, she's hot."

"Who's hot?"

Both men turned to see Catherine standing there, her eyebrows raised curiously.

"Sara," admitted Nick.

"Ah." A wry smile spread over her face. "Sorry, I kind of think she's off the market. To you, anyway."

Warrick analysed the smug look in front of him. "You know something."

She blinked at him. "I know lots of things. Not many of them are about Sara."

"Yeah, but you know this. Is there something going on between her and Grissom?"

"Mr and Mrs 'We bring a new definition to the word workaholic'?"

"Cath... really, come on, are they together?"

"Don't think so."

"Do they have a history?"

"No comment."

"Well _that_ means yes."

"Not necessarily..."

"Doesn't _anyone_ in this lab know how to mind their own business?"

They turned to the voice from the doorway in shock. "Sara..."

To the men's surprise, she was laughing at them. "It's okay. I'm almost surprised it's taken you this long, Catherine was curious right from day one."

"So you and Grissom..."

She pulled the two sides of her mouth together in a gesture of amusement, going over and opening her locker, her back to the others, purposefully keeping silent. Catherine laughed, while the others begged.

"Come on Sara... we're dying of curiosity here."

"I'll make sure to go to your funeral." She turned round, and at Nick's puppy-dog expression decided to take pity on them. "Okay, okay. Grissom and I used to be together." She turned to Catherine, and suddenly an expression of utter happiness took over her. "And, hopefully, will be again very soon, if our date tomorrow night goes well."

Catherine also lit up. "He finally asked you?"

"I asked him. We're going to an Italian restaurant, and then a concert..."

"And then a night back at your place?"

"Catherine!"


End file.
